Controle químico da ferrugem alaranjada na cultura da cana-de-açúcar
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Data
2016-05-23
Autores
Collette, Lúcio de Paula [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A ferrugem alaranjada, causada por Puccinia kuehnii, é uma importante doença na cultura da cana-de-açúcar, causando danos econômicos significativos aos produtores. É responsável por 20-40 % de perda em toneladas de cana por hectare e, além disso, provoca redução no teor de sacarose nos colmos. Diante desse contexto, o objetivo desse estudo foi determinar a eficácia dos fungicidas fluxapiroxade, do grupo químico carboxamida, com formulação de fluxapiroxade 300 g L-1 e a formulação contendo o fluxapiroxade + piraclostrobina (167 + 333 g L-1), comparados com os fungicidas padrões piraclostrobina + epoxiconazol (133 + 50 g L-1) e azoxistrobina + ciproconazol (200 + 80 g L-1). Para tal, foram conduzidos quatro experimentos, em condições de campo, no município de Santa Rita do Passa Quatro, estado de São Paulo, entre os meses de novembro de 2012 a abril de 2014. Foram empregadas as cultivares RB72454 e SP813250, plantadas no espaçamento 1,5 m entre linhas. Os tratamentos avaliados e as dosagens (em mL de produto comercial por hectare) foram: fluxapiroxade (167, 233, 300); fluxapiroxade + piraclostrobina (350), epoxiconazol + piraclostrobina (1000) e ciproconazol + azoxistrobina (300). O fungicida ciproconazol + azoxistrobina foi acrescido de 600 mL do óleo mineral Nimbus, enquanto nos demais fungicidas adicionou-se o óleo mineral Assist a 500 mL ha-1. As aplicações dos fungicidas, em número de três, e em intervalos mensais, deram-se mediante pulverizador costal pressurizado a CO2, com 30 lb-pol2, com bicos tipo leque Teejet 8002, e volume equivalente a 150 L.ha-1. Um tratamento correspondente à testemunha não recebeu aplicação com fungicida. Adotou-se o delineamento de blocos casualizados, com quatro repetições. Cada unidade experimental foi representada por parcelas constituídas por 6,0 m de largura e 10 m de comprimento, totalizando uma área de 60,0 m². As avaliações consistiram na determinação dos índices severidade dos sintomas, empregando-se escala de notas, em número de cinco avaliações. Também foi determinada a produtividade das plantas, em termos de tonelada de colmos de cana-de-açúcar por hectare. Com os dados de severidade foi calculada a área abaixo da curva de progresso da doença (AACPD). Após análise de variância, as médias foram comparadas por meio de teste de médias, empregando-se o teste Scott-Knott a 5% de probabilidade. Todos os fungicidas, independente se isolados ou em misturas, de forma geral demonstraram eficiência quando aplicados previamente ao aparecimento de sintomas da doença, em cana da cultivar SP813250, a qual apresentou baixo índice de severidade da doença. Porém, quando aplicados em plantas já sintomáticas, da cultivar RB72454, verificou-se um comportamento diferenciado dos tratamentos, com destaque para fluxapiroxade 300 g L-1 que, em doses superiores a 233 mL pc ha-1, foi estatisticamente semelhante aos padrões piraclostrobina + epoxiconazol e azoxistrobina + ciproconazol. O fungicida fluxapiroxade + piraclostrobina (167 + 333 g L-1), na dose de 350 mL pc ha-1 foi o mais eficiente, sendo superior aos padrões, independente das condições avaliadas.
Orange rust, caused by Puccinia kuehnii, is an important disease in the sugarcane crop, causing significant economic damage to farmers. It’s responsible for the loss of 20 – 40% tons of sugarcane per hectare, and furthermore causes a reduction in sucrose content in the stems. In this context, the objective of this study was to determine the effectiveness of fluxapyroxad fungicides, from carboxamide chemical group, with fluxapyroxad formulation 300 g L -1 , and the formulation containing fluxapyroxad + pyraclostrobin ( 333 + 167 g l-1) , compared with the standards fungicides pyraclostrobin + epoxiconazole ( 133 50 + g L -1 ) and azoxystrobin + cyproconazole (200 + 80 g L -1 ). To this, four experiments were conducted under field conditions at the municipality of Santa Rita do Passa Quatro, state of São Paulo, between November 2012 to April 2014. It was used RB72454 and SP813250 cultivars, planted with 1,5 m between rows. The treatments evaluated and dosages (in mL of commercial product per hectare) were: fluxapyroxad (167, 233, 300); fluxapyroxad + pyraclostrobin (350), epoxiconazole + pyraclostrobin (1000) and azoxystrobin + cyproconazole (300). For the cyproconazole + azoxystrobin fungicide was added 600 mL of Nimbus mineral oil, while the other fungicides were added the mineral oil Assist at 500 mL ha-1. The applications of fungicides, applied three times, and with monthly intervals, were done by CO2 backpack applicator, with 30 lb-pol2, nozzles type Teejet 8002, and volume equivalent to 150 L.ha-1. A corresponding treatment as check received no fungicide application. A randomized block design with four replications was adopted. Each sample unit was represented by plots with 6.0 m width and 10 m length, with a total area of 60.0 m². The evaluations consisted in determining the rates the severity of symptoms, using grading scale in number of five evaluations. Also was determined the productivity of the plants in terms of tons of sugarcane stems per hectare.The severity data were transformed into area under the disease progress curve (AUDPC). After analysis of variance, the means were compared with means test, using the Scott-Knott test at 5% probability. All fungicides, regardless of isolated or in mixtures, demonstrated effectiveness when applied prior to the onset of symptoms of the disease in sugarcane cultivar SP813250, which showed low level of disease severity. However, when applied in already symptomatic plants, cultivar RB72454, there was a different behavior of the treatments, especially fluxapyroxad 300 g L-1 that, at doses higher than 233 mL pc ha-1 was statistically similar to standards pyraclostrobin + epoxiconazole and cyproconazole + azoxystrobin. The fungicide fluxapyroxad + pyraclostrobin (167 + 333 g L-1), at dose of 350 ml pc ha-1 was the most efficient, being higher than the standards, regardless of the conditions evaluated.
Orange rust, caused by Puccinia kuehnii, is an important disease in the sugarcane crop, causing significant economic damage to farmers. It’s responsible for the loss of 20 – 40% tons of sugarcane per hectare, and furthermore causes a reduction in sucrose content in the stems. In this context, the objective of this study was to determine the effectiveness of fluxapyroxad fungicides, from carboxamide chemical group, with fluxapyroxad formulation 300 g L -1 , and the formulation containing fluxapyroxad + pyraclostrobin ( 333 + 167 g l-1) , compared with the standards fungicides pyraclostrobin + epoxiconazole ( 133 50 + g L -1 ) and azoxystrobin + cyproconazole (200 + 80 g L -1 ). To this, four experiments were conducted under field conditions at the municipality of Santa Rita do Passa Quatro, state of São Paulo, between November 2012 to April 2014. It was used RB72454 and SP813250 cultivars, planted with 1,5 m between rows. The treatments evaluated and dosages (in mL of commercial product per hectare) were: fluxapyroxad (167, 233, 300); fluxapyroxad + pyraclostrobin (350), epoxiconazole + pyraclostrobin (1000) and azoxystrobin + cyproconazole (300). For the cyproconazole + azoxystrobin fungicide was added 600 mL of Nimbus mineral oil, while the other fungicides were added the mineral oil Assist at 500 mL ha-1. The applications of fungicides, applied three times, and with monthly intervals, were done by CO2 backpack applicator, with 30 lb-pol2, nozzles type Teejet 8002, and volume equivalent to 150 L.ha-1. A corresponding treatment as check received no fungicide application. A randomized block design with four replications was adopted. Each sample unit was represented by plots with 6.0 m width and 10 m length, with a total area of 60.0 m². The evaluations consisted in determining the rates the severity of symptoms, using grading scale in number of five evaluations. Also was determined the productivity of the plants in terms of tons of sugarcane stems per hectare.The severity data were transformed into area under the disease progress curve (AUDPC). After analysis of variance, the means were compared with means test, using the Scott-Knott test at 5% probability. All fungicides, regardless of isolated or in mixtures, demonstrated effectiveness when applied prior to the onset of symptoms of the disease in sugarcane cultivar SP813250, which showed low level of disease severity. However, when applied in already symptomatic plants, cultivar RB72454, there was a different behavior of the treatments, especially fluxapyroxad 300 g L-1 that, at doses higher than 233 mL pc ha-1 was statistically similar to standards pyraclostrobin + epoxiconazole and cyproconazole + azoxystrobin. The fungicide fluxapyroxad + pyraclostrobin (167 + 333 g L-1), at dose of 350 ml pc ha-1 was the most efficient, being higher than the standards, regardless of the conditions evaluated.
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Palavras-chave
Puccinia kuehnii, Saccharum spp., Controle químico, Chemical control